The present invention relates generally to a system and method of delivering an endoluminal prosthesis within a body lumen. More particularly the present invention provides a delivery device retaining an endoluminal prosthesis during delivery and additionally for the deployment of the endoluminal prosthesis at a target site within the lumen.
Endoluminal prostheses are typically used to repair, replace, or otherwise correct a diseased or damaged blood vessel. An artery or vein may be diseased in a variety of ways. The prosthesis may therefore be used to prevent or treat a wide variety of defects such as stenosis of the vessel, thrombosis, occlusion, or an aneurysm.
One type of endoluminal prosthesis used in treatment and repair of diseases in various blood vessels is a stent. A stent is a generally longitudinal tubular device which is useful to open and support various lumens in the body. For example, stents may be used in the vascular system, urogenital tract and bile duct, as well as in a variety of other applications in the body. Endovascular stents have become widely used for the treatment of stenosis, strictures, and aneurysms in various blood vessels. These devices are implanted within the vessel to open and/or reinforce collapsing or partially occluded sections of the vessel.
Stents are generally open ended and are radially expandable between a generally unexpanded insertion diameter and an expanded implantation diameter which is greater than the unexpanded insertion diameter. Stents are often flexible in configuration, which allows them to be inserted through and conform to tortuous pathways in the blood vessel. The stent is generally inserted in a radially compressed state and expanded either through a self-expanding mechanism, or through the use of balloon catheters.
A graft is another type of endoluminal prosthesis which is used to repair and replace various body vessels. Whereas a stent provides structural support to hold a damaged vessel open, a graft provides an artificial lumen through which blood may flow. Grafts are tubular devices which may be formed of a variety of materials, including textile and non-textile materials. Grafts also generally have an unexpanded insertion diameter and an expanded implantation diameter which is greater than the unexpanded diameter.
It is also known to combine a stent and a graft to form a composite endoluminal prosthesis. Such a composite medical device provides additional support for blood flow through weakened sections of a blood vessel. In endovascular applications the use of a stent/graft combination is becoming increasingly important because the combination not only effectively allows the passage of blood therethrough, but also ensures the implant will remain open.
It is also known to provide delivery systems for delivering such prostheses intraluminally. These delivery systems generally include catheters with the prosthesis removably mounted to the distal end of the catheter. Quite often a catheter, introducer sheath, or other similar retaining means, is disposed over the prosthesis to removably support the prosthesis on the catheter. Once the prosthesis is situated in the target site in the lumen, the catheter is removed from the prosthesis.
In order to activate the prosthesis to its expanded implantation diameter, however, it is usually required to pull the sheath or retaining means away from the prosthesis to allow the expansion. The catheter typically retains and delivers the prostheses in a radially contracted state in its unexpanded insertion diameter, and removal of the catheter sheath allows expansion to the expanded implantation diameter.
Delivery and removal of the catheter sheath, however, to implant and/or activate the prosthesis presents several problems. First, catheter movement can disturb or move the introducer sheath at the wound site where the catheter is inserted into the vessel, thereby resulting in premature deployment of the prosthesis. Secondly, in tortuous anatomy, the added friction caused by rubbing the outer catheter against the vessel can make delivery and deployment of the prosthesis difficult. The translation of control movements from the proximal to the distal end of the catheter is imprecise, jerky and in some instances impossible due to the increased friction caused by tortuosity. Thirdly, delivery of the sheathed prosthesis can create trauma to the endothelium over the entire length of the catheter.
It is therefore desirous to provide an endoluminal prosthetic delivery system which delivers and activates an endoluminal prosthesis to its expanded implantation diameter without requiring removal of the catheter sheath in order to expand the prosthesis.
It is an advantage of the present invention to provide a catheter delivery system which delivers an endoluminal prosthesis to a target site without requiring the removal of an outer sheath or retaining structure.
It is also an advantage of the present invention to provide a delivery system for an endoluminal prosthesis which provides for delivery and expansion while still contained within the catheter sheath.
It is also an advantage of the present invention to provide an endoluminal prosthesis delivery system of reduced profile for effective delivery of a prosthesis through narrow body vessels.
It is a further advantage of the present invention to provide an endoluminal prosthesis delivery system which can remain implanted in a body vessel with the prosthesis.
In efficient attainment of these advantages, the present invention provides an endoluminal prosthesis delivery system comprising a tubular endoluminal prosthesis having a luminal surface and an opposed exterior surface, said prosthesis being radially expandable from a compressed condition under a first radially expansive force and a second radially expansive force greater than said first expansive force; and a delivery sheath maintaining said prosthesis in said compressed condition, said delivery sheath possessing a yield strength greater than said first expansive force of said prosthesis, and less than said second expansive force.
The present invention also provides a method of implanting an endoluminal prosthesis comprising loading a tubular endoluminal prosthesis in a reduced diameter in a compressed condition within a delivery sheath, said prosthesis being radially expandable under a first radially expansive force and a second radially expansive force greater than said first radially expansive force, said delivery sheath having a yield strength sufficient to retain said prosthesis in reduced diameter; intraluminally delivering said prosthesis to an implantation site wherein said second radially expansive force of said prosthesis is activated, said second radially expansive force being sufficient to surpass said yield strength of said delivery sheath.
In another method of implanting the prosthesis, a radially expansive force may be applied to the prosthesis by a balloon catheter, said radially expansive force being sufficient to surpass said yield strength of said delivery sheath.